Monitoring systems that include a monitor for displaying video image of a monitored area to monitor a moving object(s) such as persons included in the image are widely used. Further, it is known to detect a moving object from the image and, based on the detection position information obtained thereby, generate a movement line (movement trajectory) representing the movement path of the moving object (see JP2011-243155A). If the movement line is displayed superimposed on the real-time image by use of such movement line generation technology, it is possible to grasp the moving state of the moving object properly by viewing the displayed movement line together with the moving object included in the image, and thus, the efficiency of the monitoring work can be improved.
In a case where a movement line of a moving object is displayed superimposed on the real-time image as described above, if the movement line is formed by merely connecting the detection positions in chronological order, the movement line may significantly depart from the actual movement path of the moving object because the detection positions may include “noise” caused by an error in the moving object detection process. Therefore, it is desirable to remove the noise caused by an error in the moving object detection process and generate a determined movement line optimized as the movement path of the moving object based on the detection positions having the noise removed.
However, it takes time to perform the process of generating the determined movement line, and this may cause the movement line to be displayed with a significant delay relative to the movement of the moving object (such as a person). In such a case, there is a problem that the movement path is not displayed to closely follow the moving object and thus a user may feel a sense of incongruity. Further, in the case where the movement line is not drawn to closely follow the moving object, it becomes difficult to properly grasp the moving state of the moving object, creating a problem that the efficiency of the monitoring work is decreased.